Is Omicron 'mild'? We don't know yet
Despite a widespread belief, we have no idea whether the Omicron variant induces milder disease than other variants. It's too early to say
Some people are predisposed to believe the worst; they’re natural pessimists. Or they’re pessimists about one particular thing: climate change, terrorism, the economy... They’ll latch onto any piece of bad news and turn into Private Frazer from Dad’s Army.
And then there’s nature’s optimists, who are more willing to believe good news than bad. The Professor Farnsworths, if you will.
So it is with the Covid-19 pandemic. Some people are understandably desperate for good news after a difficult two years. Some are ground down, scared and pessimistic.
Both of these attitudes are grabbed by Covid conspiracy theorists and sceptics, too.
Any bad news is presented as evidence that ‘they’ will never let the pandemic end. Every new variant or bad outcome is greeted with glee and smug satisfaction. See, we told you!
Any good news is a reason to immediately stop vaccinations, end masking remove all pandemic restrictions. Anything else is just fearmongering.
And the same is true of Omicron.
On the one hand, the suggestion that Omicron evades immunity, whether induced by vaccination or recovery, fits right into some pre-cooked antivax narratives. I’ve already heard “Oh, a variant that means the ‘naturally immune’ are at risk. How convenient!” and '“the Global Elites would never give up power now they have it”, though I’m pretty sure that the global elites were globally elite both before and during the pandemic and will continue to be globally elite afterwards. Or “See, the vaccines are useless but you still think we should get vaccinated!”
But maybe worse is the mirage of good news.
For some reason, there’s a widespread belief that that the Omicron variant is mild , very mild or even ‘super-mild’.
This belief has been seized on by Covid-sceptics to oppose any new restrictions. But it’s spread much wider than that, and lots of very sensible people believe that Omicron is a much milder variant of the virus than Delta or Alpha were.
Any tweet about Omicron is flooded with replies claiming “all the data shows Omicron is really mild”, “it’s the mildest variant yet” and
The fairytale ending
“Like all viruses, Covid will eventually become milder and milder as it evolves until it turns into a common cold”
That’s the fairytale pandemic ending that a lot of people seem to believe; that naturally, the coronavirus will cause less virulent disease due to evolution. Omicron, they say, is a good thing. It will spread quickly and painlessly and go away, because that’s how it’s supposed to work.
But there’s really no reason to believe that’s how it will go. This virus is mostly infectious before it causes any symptoms; by the time a host dies of Covid-19, they often are no longer infected by the virus but are instead suffering from the damage it caused. From an evolutionary point of view, a mild variant has no major advantage over a severe one.
Covid-19 will become milder in practice as our own immune systems learn to fight it, from vaccination, infection or a combination of both. That’s the only real path from pandemic to endemic.
But coronavirus variants can be more or less severe. Alpha and Delta both appeared to be a bit more severe than the original virus.
What’s a ‘mild’ variant?
What does it even mean to say that a coronavirus variant is ‘mild’? Well, it could mean a few different things:
People who catch it are more likely to be asymptomatic than other variants
People who develop mild symptoms tend to have milder mild symptoms
People who catch it are less likely to need hospitalisation
People who develop severe disease are less likely to die
These things are related but not identical. Conceivably, a coronavirus variant could cause fewer symptomatic cases but a higher number of severe cases in people who do develop symptoms. Or a variant could display a different disease profile, eg riskier for children.
These different things have been conflated in early coverage of Omicron out of South Africa.
What’s Special About South Africa?
Back in late Spring 2020 as New York City’s first horrific Covid wave subsided, some celebrated the end of the pandemic, insisting that surely the city had reached Herd Immunity. “Everyone’s had it!”
It wasn’t true, and it hasn’t been true in almost any country that’s claimed to have reached immunity through infection alone.
But by late 2021, after three major Covid waves and a 36% vaccination rate, South Africa might have got there. It’s likely that the vast majority of South Africans have some level of immunity to Covid-19.
Omicron appears to have a meaningful level of immune evasion, meaning people who have Covid immunity from vaccination or previous infection by another variant are more likely to catch Omicron than they were to catch, say, Delta. So when we talk about South Africa, we’re talking about somewhere almost everyone already has some level of Covid immunity.
Why do people keep saying Omicron is mild?
“Most Omicron cases are mild”
Well, yes. This is true. Most Delta cases were mild too. And so were most Alpha cases, and most wildtype. Most Omicron cases are mild because most Covid-19 cases are mild.
Some very bad public health communicators, like (unfortunately) the World Health Organisation have said things like “most Omicron cases are mild” which is true but confusing to the public, who hear “Omicron is less dangerous than other variants”.
“A doctor in South Africa said it’s mild”
This one is partly down to news organisations. Doctors in South Africa, like Dr. Angelique Coetzee, report on the cases they’ve personally seen in the couple of weeks since Omicron emerged:
"Most of them are seeing very, very mild symptoms and none of them so far have admitted patients to surgeries. We have been able to treat these patients conservatively at home," she said.
Coetzee, who is also on the Ministerial Advisory Committee on Vaccines, said unlike the Delta so far patients have not reported loss of smell or taste and there has been no major drop in oxygen levels with the new variant.
Her experience so far has been that the variant is affecting people who are 40 or younger. Almost half of the patients with Omicron symptoms that she treated were not vaccinated.
Reading her full comments in context, it’s pretty clear she’s talking about her first-hand clinical experience at her practice. She saw around 40 patients, mostly young, more than 50% vaccinated, and none of them needed oxygen or hospitalisation. That’s… not a big surprise for the profile of those patients .
But some of the coverage made it sound like she was talking about all Omicron patients in South Africa, leading to headlines claiming Omicron was always mild in everyone and that nobody had gone to hospital with it.
In reality, hospital beds are filling up fast:
Dr. Fareed Abdullah, who heads the South African Medical Research Council, says the surges are already happening in Johannesburg and Tshwane.
Hospitals in South Africa’s Gauteng province, which contains two of the country’s biggest cities, are packed with people infected with the omicron variant. Doctors say most of the patients haven’t been vaccinated, and an alarming number of them are children under the age of five-years-old.
“There’s been a rather rapid rise in hospital admissions with patients who have COVID, whether they’re presenting with COVID pneumonia or severe COVID disease," Dr. Abdullah said.
"All of the hospitals in Tshwane are seeing an upsurge, and the COVID bed occupancy is increasing 30% to 40% per day, over the last few days,” he said.
“The data in South Africa shows it’s milder than Delta was”
This is where it gets a bit more complicated.
A LOT of people with Omicron in South Africa —probably the majority, maybe a significant majority — have already had Covid-19 in the past or been vaccinated.
Reinfections or vaccine breakthrough cases are usually milder than naïve infections. That’s why the novel coronavirus was so scary: it was new, and when our immune systems met it for the first time, they freaked out.
With more breakthrough cases, we’d expect a greater proportion of cases overall to be mild compared to a variant that didn’t re-infect very much, but that’s partly because the same people wouldn’t be catching Covid at all before Omicron.
We can illustrate this with an example. The numbers I’m using aren’t supposed to be accurate, but it gives you an idea:
Imagine a population of 1100 people, where 100 people have never had Covid, and 1000 have had it and recovered. Let’s also say that 5% of people who’ve never had Covid develop a severe case, compared to just 0.5% who’ve had it before.
Imagine Delta hits this group:
It infects the 100 naïve people plus 9% of the others (90).
5% of the 100 (5 cases) develop severe Covid
0.5% of the reinfections (zero, actually) develop severe Covid
Total: 5 severe cases out of 190 infections.
Now imagine it’s Omicron instead of Delta.
The 100 naïve people get Omicron, but 25% of the recovered people (250) catch it too.
As above, 5 of the 100 develop severe Covid
So do 0.5% of the 250 (just one).
Total: 6 severe cases out of 350 infections.
In this example, Delta seems to be more severe, with 2.6% of cases becoming severe vs just 1.7% for Omicron. But that’s because Omicron inflated the denominator: it added mild cases which wouldn’t have been cases in the first place if Omicron didn’t exist. And, of course, the numerator is higher too with Omicron, and there’s an extra hospital bed with a severe patient in it.
And here’s where it gets scary, because at least some of those 250 people are infectious now, and they can go on to spread Omicron more widely, perhaps helping to account for the variant’s very high infectivity.
Early data about South African cases being less severe was also confounded by the early Omicron cases being very young.
Now, the number of patients needing oxygen for Covid-pneumonia is rising sharply too as are ICU numbers.
We don’t know yet how severe Omicron is in naïve patients. There are areas in the world with both low vaccination rate and relatively low past infection; these are the places most at risk from Omicron.
But Omicron seems to be spreading SO fast that it can generate enough new severe cases to overwhelm hospitals, perhaps very quickly, even in a population with very high levels of past infection and vaccination.
Two important pieces of reading I’d recommend on Omicron:
John Burn-Murdoch’s thread on Delta in SA, which was the source for the graphs above.Okay folks, time for a South Africa update, focused this time on severity of disease. First up, the report from hospitals in Tshwane (the district furthest along in Omicron wave) is essential reading, as is thread from samrc.ac.za/news/tshwane-d…
Mia Malan @miamalan[Thread] JUST IN: 1. NEW #OmicronVariant data from the Steve Biko/Tshwane District Hospital Complex via @MRCza. Tshwane = where SA's Omicron outbreak started 1. Data = for the 1st 2 weeks of the outbreak (14-29 Nov) 2. Past 5 days (29 Nov-3 Dec) = exponential increase in cases https://t.co/rbjpjEOQqQ
I want Omicron to be mild. I hope Omicron is mild. But we don’t have the data to know that for sure yet. And given how infectious it is and how successfully it’s evading immunity, even being mild might not stop a disaster in the coming weeks.
Sorry for ending on a downer and thanks for reading.
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